424 ME. T. GEAIIAM ON THE ABSOEPTION AND 



22*2 grms. were heated by the combustion-furnace, and for half an hour allowed to 

 cool gradually in dry hydrogen gas, as in the preceding experiments. The volume of 

 the platinum is 1-032 cub. centim. by calculation. In the first experiment it yielded to 

 heat and the action of the Sprengel pump 2-2 cub. centims. of a gas which burned 

 like hydrogen. In a second experiment the platinum yielded in one hour (when it 

 appeared to be exhausted) 1-7 cub. centim. of gas, found by explosion to consist of 

 hydrogen 1"52 cub. centim., and nitrogen 0*18 cub. centim. Here one volume of spongy 

 platinum appears capable of occluding 



1"48 vol. hydrogen. 



6. Wrought platinum, in the form of plate from an old crucible cut up, after washing 

 and ignition, was charged with hydrogen three times in succession. The weight of the 

 platinum was 24-1 grms,, and its volume 1*12 cub. centim. It yielded in seventy-five 

 minutes 4-19 cub. centims. of gas, and in thirty minutes further 1"5 cub. centim. 

 more, making together 5*69 cub. centims., of which 4'94 cub. centims. proved to be 

 hydrogen ; therm. 14°*2, barom. 760 millims. Not a trace of carbonic acid was found 

 in the gas before or after explosion. Again, after a second charge, 5'12 cub. centims. 

 of gas vi^ere given up in an hour, of which 4*4 were hydrogen ; and lastly, .3'76 cub. 

 centims. in an hour, of which 3-42 were hydrogen. Hence, occluded by 1 vol, wrought 

 platinum — 



5"53 vols, hydrogen, 



4'Jo „ „ 



3-83 „ „ 



The volume of occluded hydrogen is much larger than in the fused platinum, or 

 even in the spongy platinum. It exhibits a, tendency to fall oflf on repeating the expe- 

 riment. The declension in absorbing-power may possibly be connected with the reduced 

 duration of the exposure to hydrogen of the metal while cooling. 



7. Wrought platinum, which had been formed many years ago into a small tube, 

 weighing 64-8 grms., 0'322 metre in length and 5 millims. in diameter, was cut into 

 three equal lengths for convenience in placing the metal within the porcelain tube, to 

 be heated and charged with dry hydrogen. By an hour's exhaustion afterwards the 

 platinum yielded 9 '2 cub, centims. gas, of which 8*9 were hydrogen. The volume of 

 the platinum itself was 3'9 cub. centims. ; and one volume of metal had therefore 

 occluded 2'28 vols, hydrogen, measured at about 20° C. In all such experiments, be- 

 sides blowing out the free hydrogen by air, the apparatus was also thoroughly exhausted 

 by the Sprengel pump in the cold, before the occluded hydrogen was extracted. 



The lustre and appearance of the metallic platinum was not altered by the ingress of 

 the hydrogen ; but after the escape of the gas the platinum appeared whiter in colour, 

 and the surface was covered by minute blisters. 



Repeating the experiment, the gas collected by an hour's exhaustion was 8-7 cub. 

 centims., of which 8-46 cub. centims. were hydrogen. Here the metal occluded 2*8 

 vols, of hydrogen. 



